U.S. patent application number 13/754647 was filed with the patent office on 2013-08-01 for methods and apparatus for efficient spectral usage in extensible carrier deployments.
This patent application is currently assigned to Apple Inc.. The applicant listed for this patent is Apple Inc.. Invention is credited to Sassan Ahmadi.
Application Number | 20130195052 13/754647 |
Document ID | / |
Family ID | 48870158 |
Filed Date | 2013-08-01 |
United States Patent
Application |
20130195052 |
Kind Code |
A1 |
Ahmadi; Sassan |
August 1, 2013 |
METHODS AND APPARATUS FOR EFFICIENT SPECTRAL USAGE IN EXTENSIBLE
CARRIER DEPLOYMENTS
Abstract
Methods and apparatus for providing efficient spectral usage in
extensible carrier deployments. In one embodiment, the deployment
comprises a long-term evolution (LTE) or LTE-advanced (LTE-A)
network, and a reference carrier resource and one or more
extensible carrier resources are configured based at least in part
on a time and/or frequency separation. In one exemplary
implementation, one or more reference carriers are combined with
one or more carrier extensions/segments. The resulting aggregated
bandwidth can be used to, among other things, optimize overall
network operation.
Inventors: |
Ahmadi; Sassan; (Cupertino,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Apple Inc.; |
Cupertino |
CA |
US |
|
|
Assignee: |
Apple Inc.
Cupertino
CA
|
Family ID: |
48870158 |
Appl. No.: |
13/754647 |
Filed: |
January 30, 2013 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61593218 |
Jan 31, 2012 |
|
|
|
Current U.S.
Class: |
370/329 |
Current CPC
Class: |
H04L 5/0087 20130101;
H04L 5/0032 20130101; H04W 72/044 20130101; H04L 5/0048 20130101;
H04L 5/001 20130101; H04W 16/14 20130101; H04W 28/08 20130101; H04W
72/0453 20130101 |
Class at
Publication: |
370/329 |
International
Class: |
H04W 72/04 20060101
H04W072/04 |
Claims
1. A method for providing efficient spectral usage in extensible
carrier deployments, comprising: identifying one or more reference
carriers and one or more carrier extensions or segments;
aggregating the identified one or more reference carriers and the
one or more carrier extensions or segments into an aggregated band;
and provisioning the aggregated band.
2. The method of claim 1, where the identification is performed at
least by a network of base stations in a peer-to-peer manner.
3. The method of claim 1, where the identification is performed at
least by a centralized network authority.
4. The method of claim 1, where: the one or more reference carriers
comprises at least one fully configured backward compatible
reference carrier; and the one or more carrier extensions or
segments comprises only a subset of reference carrier
functionality.
5. The method of claim 4, where the one or more carrier extensions
or segments are configured without reference signals specific to
one or more cells.
6. The method of claim 5, where the one or more carrier extensions
or segments are further configured to support enhanced control
signaling based on at least one self-contained reference
signal.
7. The method of claim 4, where: the one or more carrier extensions
or segments are configured with Primary Synchronization Symbols
(PSS) or Secondary Synchronization Symbols (SSS); and the PSS and
SSS indicate a time reference associated with the one or more
carrier extensions or segments.
8. The method of claim 4, where the one or more carrier extensions
or segments are configured with demodulation reference signals and
channel state information reference signals.
9. The method of claim 8, where the channel state information
reference signals enables user equipment to perform channel
estimation and coherent detection of at least one control or data
channel.
10. The method of claim 1, where at least one or more guard band
resource blocks between the frequency bands associated with the
reference resources and the one or more extensible resources are
re-allocated for data traffic.
11. Mobile apparatus configured to implement efficient spectral
usage in a network, the apparatus comprising: a receiver; a
processor in signal communication with the receiver; and logic in
communication with the processor and configured to: identify one or
more reference carriers and one or more carrier extensions;
determine whether the one or more reference carriers is contiguous
with the one or more carrier extensions in the frequency domain;
and select one or more reception modes based at least in part on
the determination.
12. The apparatus of claim 11, where the logic is further
configured to receive, when determination indicates that the one or
more reference carriers is not contiguous with the one or more
carrier extensions, one or more synchronization signals associated
with the one or more carrier extensions.
13. The apparatus of claim 12, where the one or more carrier
extensions contains one or more user equipment specific reference
signals.
14. The apparatus of claim 11, where the logic is further
configured to receive, when the one or more reference carriers is
determined to be contiguous with the one or more carrier
extensions, synchronization signals associated with the one or more
reference carriers.
15. The apparatus of claim 11, where the logic is further
configured to receive, when the one or more reference carriers is
contiguous with the one or more carrier extensions, guard band
resource blocks at the periphery of the bandwidth comprising the
one or more reference carriers and the one or more carrier
extensions.
16. A base station apparatus for use in a long term evolution
(LTE)-enabled cellular wireless communications network, comprising:
a wireless interface, the wireless interface configured to
communicate with a plurality of wireless devices; a processor; and
a computer readable apparatus having a storage medium with at least
one computer program stored thereon, the at least one computer
program configured to, when executed on the processor, cause the
base station apparatus to: identify one or more reference carriers
provided by at least one other base station apparatus; generate at
least one or more carrier extensions; and aggregate the one or more
reference carriers and the at least one or more carrier
extensions.
17. A wireless system, the wireless system comprising a plurality
of base stations configured to provide cellular network service to
a plurality of mobile user devices, where at least a first set of
base station devices are configured to provide at least one or more
reference carriers, and where a second set of base station devices
are configured to provide at least one or more carrier extensions,
and where the first and second set of base station devices are
different.
18. The wireless system of claim 17, where the at least one or more
carrier extensions and the at least one or more reference carriers,
when aggregated, form a contiguous bandwidth.
19. The wireless system of claim 18, where the at least one or more
carrier extensions and the at least one or more reference carriers,
when aggregated, form a non-contiguous bandwidth.
20. A method of operating a mobile device within a wireless system,
comprising: evaluating one or more reference carriers and one or
more carrier extensions; based at least in part on the evaluation,
aggregating the one or more reference carriers and one or more
carrier extensions; and receiving the aggregated one or more
reference carriers and one or more carrier extensions with a single
Fast Fourier Transform (FFT) element.
Description
PRIORITY AND RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional Patent
Application Ser. No. 61/593,218 filed Jan. 31, 2012 and entitled
"METHODS AND APPARATUS FOR EFFICIENT SPECTRAL USAGE IN EXTENSIBLE
CARRIER DEPLOYMENTS", the foregoing being incorporated herein by
reference in its entirety.
[0002] This application is also related to co-owned, co-pending
U.S. patent application Ser. No. 13/______ filed contemporaneously
herewith on Jan. 30, 2013, and entitled "METHODS AND APPARATUS FOR
ENHANCED SCRAMBLING SEQUENCES", which claims priority to U.S.
Provisional Application Ser. No. 61/593,208 filed on Jan. 31, 2012,
and entitled "METHODS AND APPARATUS FOR ENHANCED SCRAMBLING
SEQUENCES", each of the foregoing being incorporated herein by
reference in its entirety.
COPYRIGHT
[0003] A portion of the disclosure of this patent document contains
material that is subject to copyright protection. The copyright
owner has no objection to the facsimile reproduction by anyone of
the patent document or the patent disclosure, as it appears in the
Patent and Trademark Office patent files or records, but otherwise
reserves all copyright rights whatsoever.
BACKGROUND
[0004] 1. Technical Field
[0005] The present disclosure relates generally to the field of
wireless networks and telecommunications. More particularly, in one
exemplary embodiment, the present disclosure describes
configuration and usage of extensible carrier resources within a
wireless (e.g., cellular) network.
[0006] 2. Description of Related Technology
[0007] Incipient research in spectral usage and deployment address
an ever increasing demand for higher capacity and higher data rates
in cellular networks. Significant areas of interest include
modifications to existing data and control information transmission
structures (also referred to throughout as "carriers"). For
example, standardization efforts for 3GPP (3rd Generation
Partnership Project) Long Term Evolution (LTE) Release 11 have been
directed to partially-configured carrier structures within
non-backward compatible configurations.
[0008] Within the context of 3GPP LTE Release 11, proposed and/or
existing solutions for carrier design are required to support
operation in the following scenarios: (i) synchronized carriers
(i.e., where the legacy and segment/extension carriers are
synchronized in time and frequency), and (ii) unsynchronized
carriers (i.e., where the legacy and segment/extension carriers are
not synchronized in time and/or frequency such that separate
synchronization processing is required in the receiver). More
directly, carrier synchronization has a direct impact on the
processing burden of the receiver.
[0009] Generally, network operators struggle with adding new
spectrum within coverage areas which have existing spectral
deployments. While synchronized carriers are preferred to reduce
overall receiver complexity, unsynchronized carriers are easier to
deploy. Existing solutions for improving network coverage rely on
adding more spectrum; however, incipient research is directed to
more efficient spectral usage and/or additional optimizations which
may be possible, with larger aggregated bandwidths.
[0010] Hence, improved solutions are needed for configuration and
usage of extensible carrier resources within a wireless (e.g.,
cellular) networks. Ideally, such solutions for carrier deployment
should optimize energy efficiency, provide flexible spectrum usage,
enable heterogeneous network deployments, and/or enable machine
type communications.
SUMMARY
[0011] The present disclosure satisfies the aforementioned needs by
providing, inter alia, improved apparatus and methods for providing
efficient spectral usage in extensible carrier deployments.
[0012] Firstly, a method for providing efficient spectral usage in
extensible carrier deployments is disclosed. In one embodiment, the
method includes: identifying one or more reference carriers and one
or more carrier extensions/segments; aggregating the identified one
or more reference carriers and one or more carrier
extensions/segments; and provisioning the aggregated one or more
reference carriers and one or more carrier extensions/segments.
[0013] In a second embodiment, the method includes: identifying one
or more reference carriers and one or more carrier extensions or
segments; aggregating the identified one or more reference carriers
and the one or more carrier extensions or segments into an
aggregated band; and provisioning the aggregated band.
[0014] A base station device for providing efficient spectral usage
in extensible carrier deployments is also disclosed. In one
embodiment, the base station is capable of operation within a
cellular (e.g., LTE) network, and includes logic configured to
aggregate one or more reference carriers and one or more carrier
extensions/segments.
[0015] A computer readable apparatus is further disclosed. In one
embodiment, the apparatus includes a storage medium having at least
one computer program disposed thereon, the at least one program
being configured to, when executed, provide efficient spectral
usage in extensible carrier deployments.
[0016] An integrated circuit (IC) is also disclosed. In one
embodiment, the integrated circuit includes logic which is
configured to provide efficient spectral usage in extensible
carrier deployments.
[0017] A wireless system is further disclosed. In one embodiment,
the system includes a plurality of base stations and a plurality of
mobile user devices. The base station devices are configured to
provide efficient spectral usage in extensible carrier
deployments.
[0018] A method of operating a mobile device is additionally
disclosed. In one embodiment, the method includes evaluating a
carrier received by the mobile device, and selectively adjusting
one or more reception modes accordingly.
[0019] A method for providing efficient spectral usage in
extensible carrier deployments is disclosed. In one embodiment, the
method includes: identifying one or more reference carriers and one
or more carrier extensions or segments; aggregating the identified
one or more reference carriers and the one or more carrier
extensions or segments into an aggregated band; and provisioning
the aggregated band.
[0020] In some variants, the identification is performed at least
by a network of base stations in a peer-to-peer manner.
[0021] In other variants, the identification is performed at least
by a centralized network authority.
[0022] In still other variants, the one or more reference carriers
comprises at least one fully configured backward compatible
reference carrier; and the one or more carrier extensions or
segments comprises only a subset of reference carrier
functionality. In certain instances, the one or more carrier
extensions or segments are configured without reference signals
specific to one or more cells. Moreover, in certain cases, the one
or more carrier extensions or segments are further configured to
support enhanced control signaling based on at least one
self-contained reference signal.
[0023] In still other variants, the one or more carrier extensions
or segments are configured with Primary Synchronization Symbols
(PSS) or Secondary Synchronization Symbols (SSS); and the PSS and
SSS indicate a time reference associated with the one or more
carrier extensions or segments.
[0024] In certain variants, the one or more carrier extensions or
segments are configured with demodulation reference signals and
channel state information reference signals. For instance, the
channel state information reference signals enables user equipment
to perform channel estimation and coherent detection of at least
one control or data channel.
[0025] In some implementations, at least one or more guard band
resource blocks between the frequency bands associated with the
reference resources and the one or more extensible resources are
re-allocated for data traffic.
[0026] Mobile apparatus configured to implement efficient spectral
usage in a network is disclosed. In one embodiment, the mobile
apparatus includes: a receiver; a processor in signal communication
with the receiver; and logic in communication with the processor.
In one exemplary embodiment, the logic is configured to: identify
one or more reference carriers and one or more carrier extensions;
determine whether the one or more reference carriers is contiguous
with the one or more carrier extensions in the frequency domain;
and select one or more reception modes based at least in part on
the determination.
[0027] In some variants, the logic is further configured to
receive, when determination indicates that the one or more
reference carriers is not contiguous with the one or more carrier
extensions, one or more synchronization signals associated with the
one or more carrier extensions. In one such example, the one or
more carrier extensions contains one or more user equipment
specific reference signals.
[0028] In other variants, the logic is further configured to
receive, when the one or more reference carriers is determined to
be contiguous with the one or more carrier extensions,
synchronization signals associated with the one or more reference
carriers.
[0029] Still other implementations may be further configured to
receive, when the one or more reference carriers is contiguous with
the one or more carrier extensions, guard band resource blocks at
the periphery of the bandwidth comprising the one or more reference
carriers and the one or more carrier extensions.
[0030] A base station apparatus for use in a long term evolution
(LTE)-enabled cellular wireless communications network is
disclosed. In one embodiment, the base station apparatus includes:
a wireless interface, the wireless interface configured to
communicate with a plurality of wireless devices; a processor; and
a computer readable apparatus having a storage medium with at least
one computer program stored thereon. In one exemplary embodiment,
the at least one computer program is configured to, when executed
on the processor, cause the base station apparatus to: identify one
or more reference carriers provided by at least one other base
station apparatus; generate at least one or more carrier
extensions; and aggregate the one or more reference carriers and
the at least one or more carrier extensions.
[0031] A wireless system is disclosed. In one embodiment, the
wireless system includes a plurality of base stations configured to
provide cellular network service to a plurality of mobile user
devices, where at least a first set of base station devices are
configured to provide at least one or more reference carriers, and
where a second set of base station devices are configured to
provide at least one or more carrier extensions, and where the
first and second set of base station devices are different.
[0032] In some variants, the at least one or more carrier
extensions and the at least one or more reference carriers, when
aggregated, form a contiguous bandwidth. In certain cases, the at
least one or more carrier extensions and the at least one or more
reference carriers, when aggregated, form a non-contiguous
bandwidth.
[0033] A method of operating a mobile device within a wireless
system is disclosed. In one exemplary embodiment, the method
includes: evaluating one or more reference carriers and one or more
carrier extensions; based at least in part on the evaluation,
aggregating the one or more reference carriers and one or more
carrier extensions; and receiving the aggregated one or more
reference carriers and one or more carrier extensions with a single
Fast Fourier Transform (FFT) element.
[0034] Other features and advantages of the present disclosure will
immediately be recognized by persons of ordinary skill in the art
with reference to the attached drawings and detailed description of
exemplary embodiments as given below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] FIG. 1 is a logical flow diagram depicting one embodiment of
a generalized method for providing efficient spectral usage in
extensible carrier deployments, in accordance with the present
disclosure.
[0036] FIG. 2 is a graphical representation of a first exemplary
scenario where a reference carrier and one or more carrier
extensions/segments are not contiguous in the frequency domain, the
foregoing illustrative of various principles of the present
disclosure.
[0037] FIG. 3 is a graphical representation of a second exemplary
scenario where a reference carrier and one or more carrier
extensions/segments are contiguous in the frequency domain, the
foregoing illustrative of various principles of the present
disclosure.
[0038] FIG. 4 is a graphical representation of a third exemplary
scenario where the reference carrier and the one or more carrier
extensions/segments are contiguous in the frequency domain and
where backward compatibility is not required, the foregoing
illustrative of various principles of the present disclosure.
[0039] FIG. 5 illustrates an exemplary embodiment of a user or
client apparatus in accordance with the principles described
herein.
[0040] FIG. 6 illustrates an exemplary embodiment of a base station
apparatus in accordance with the principles described herein.
[0041] All FIGS. .COPYRGT.Copyright 2013 Apple Inc. All rights
reserved.
DETAILED DESCRIPTION
[0042] Reference is now made to the drawings, wherein like numerals
refer to like parts throughout.
Overview
[0043] In one exemplary embodiment, a reference carrier resource
and one or more extensible carrier resources are configured based
at least in part on a time and/or frequency separation. Within the
context of exemplary embodiments described herein, the reference
carrier resources and/or one or more extensible carrier resources
are aligned and aggregated for use.
[0044] In one exemplary implementation, the one or more extensible
carrier resources are further configured without Cell-specific
Reference Signals (CRS). As described in greater detail
hereinafter, CRS equivalent functionality can be determined from
alternate data and control channel signaling. For example, certain
properties of CRS can be replaced with equivalent properties of
e.g., the Demodulation Reference Signals (DM-RS) and Channel State
Information Reference Signals (CSI-RS).
[0045] In one such variant, one or more extensible carrier
resources may be used in combination with a reference carrier. For
deployments where there is insufficient time/frequency
synchronization between the reference carrier resource and the one
or more extensible carrier resources, the Primary Synchronization
Symbols (PSS) and/or Secondary Synchronization Symbols (SSS) are
additionally configured on the one or more extensible carrier
resources.
[0046] As previously alluded to, the Demodulation Reference Signals
(DM-RS) and Channel State Information Reference Signals (CSI-RS)
may be configured on the one or more extensible carrier resources
to provide functional equivalence to legacy CRS signaling. For
example, rather than performing mobility measurements and carrier
activation/deactivation measurements on CRS, such measurements can
be performed based on an appropriately configured DM-RS and/or
CSI-RS.
[0047] The CSI-RS is configured to mitigate interference with
data/control transmissions in the same cell; however, the CSI-RS
may interfere with carrier resources (reference or extensible
resources) of neighboring cells. Accordingly, certain interference
management techniques described herein are used as necessary to
reduce inter-cell CSI-RS interference (e.g., muting,
non-overlapping assignments, etc.).
[0048] Finally, in yet another variant, the guard band resource
blocks between the reference resources and the one or more
extensible resources may be re-allocated for data traffic.
Re-allocation of guard band resource blocks for data traffic
significantly increases spectral utilization efficiency.
Configuration and Usage of Carrier Resources--
[0049] As previously stated, within the context of 3GPP LTE Release
11, proposed and/or existing solutions for carrier design are
required to support both synchronized and unsynchronized carrier
deployments. Accordingly, in one exemplary use scenario, the
network is configured for operation without Cell specific Reference
Signals (CRS-free). In some circumstances, the network may further
support enhanced control signaling with self-contained reference
signals and dynamic configurability of synchronization and other
reference signal types.
[0050] As described in greater detail herein, carrier types are
disclosed for both extension carriers and carrier segments. As used
herein, the term "reference carrier" refers to a fully-configured
backward compatible carrier. As used herein, the term "extension
carrier" refers to a carrier which cannot be operated as a single
stand-alone carrier; rather, extension carriers must be part of a
component carrier set that includes at least one fully-configured
carrier. Similarly, as used herein, the term "carrier segments"
refers to additional bandwidth extensions for a compatible carrier.
Carrier segments provide a mechanism to utilize frequency resources
in deployment cases where new transmission bandwidths are needed in
a backward compatible manner complementing carrier aggregation
schemes.
[0051] Within the context of the present disclosure, various
schemes are disclosed for reducing the additional Physical Downlink
Control Channel (PDCCH) transmission overhead that would be
required for legacy PDCCH schemes while also enabling small
transport block sizes within the carrier segments. Carrier segments
enable aggregation of additional resource blocks within a component
carrier, while still retaining backward compatibility over the
original carrier bandwidth. Carrier segments can be adjacent to,
and/or linked to a fully-configured carrier. In one such
embodiment, carrier segments do not include synchronization
signals, system information or paging information.
[0052] As a brief aside, CRS-free operation provides multiple
benefits for network operation. Firstly, CRS-free carrier types
reduce overall interference attributed to the CRS transmissions
(both inter-cell and intra-cell interference). Moreover, resources
that would otherwise be reserved for CRS operation can be allocated
to e.g., data or control traffic. Finally, CRS-free carrier types
can reduce overall power consumption (CRS transmissions are always
on, even when the cell is not fully loaded).
[0053] Unfortunately, CRS-free operation has certain deficiencies
which must be addressed. Specifically, CRS traditionally handles
multiple important functions including without limitation: channel
estimation, mobility measurements, and time/frequency tracking.
Accordingly, alternative solutions for the foregoing functions are
required for CRS-free operation.
[0054] One embodiment addresses these deficiencies using, inter
alia, data transmission and enhanced control signaling based on
self-contained reference signals (RS). Rather than prior art
solutions which rely on a CRS, a self-contained RS can be used for
channel estimation. For example, in one such embodiment,
transmission modes are based on the Demodulation Reference Signal
(DM-RS). Other variations may include for example, device-specific
RS.
[0055] Moreover, CRS-free carriers should provide configurable
signaling structures e.g., Primary Synchronization Signaling (PSS),
Secondary Synchronization Signaling, etc.). Such configurability
may be necessary based on the deployment signals, etc. For example,
transmissions of PSS/SSS can provide time and/or frequency
synchronization capabilities; thus, systems which are closely
synchronized may reduce or eliminate PSS/SSS transmissions
altogether.
[0056] Various configurations of reference carriers, extension
carriers and carrier segments are further described herein.
Specifically, various embodiments are described with respect to
conditions and/or use scenarios (e.g., based on relative spectral
locations, time and/or frequency alignment, etc.).
Methods--
[0057] FIG. 1 illustrates one embodiment of a generalized method
100 for providing efficient spectral usage in extensible carrier
deployments, in accordance with the various principles described
herein.
[0058] At step 102 of the method 100, one or more reference
carriers and one or more carrier extensions/segments are
identified. In one approach, carrier identification is performed in
a peer-to-peer manner by the base station devices. In other
embodiments, carrier identification is performed by a centralized
network authority. For example, within 3GPP networks, peer-to-peer
communication among LTE eNBs is performed via an X2 interface,
communication between NodeBs (and between NodeBs and eNBs) is
handled via the Core Network. In other network configurations
(e.g., heterogeneous networks, etc.), communication between base
stations may require routing via the Core Network.
[0059] In one configuration, a network of base stations provides at
least one fully configured backward compatible reference carrier,
and one or more carrier extensions/segments which provide only a
subset of reference carrier functionality. In one such example, the
one or more carrier extensions/segments lack one or more
Cell-specific Reference Signals (CRS). The one or more carrier
extensions/segments only provide Demodulation Reference Signals
(DM-RS). Unlike CRS, DM-RS are specific to one or more serviced
user equipment (UE) devices.
[0060] At step 104 of the method 100, the identified one or more
reference carriers and one or more carrier extensions/segments are
aligned and/or aggregated. Generally, the process of alignment
includes shifting the one or more carrier extensions/segments in
time and/or frequency. In one exemplary embodiment, the one or more
reference carriers and one or more carrier extensions/segments are
combined into an aggregated bandwidth. In other embodiments, only
select ones of the one or more reference carriers and one or more
carrier extensions/segments are aligned and/or aggregated.
[0061] Common reasons for alignment and aggregation may include,
without limitation: network usage, network optimization, spectral
efficiency, reduced processing burden on the population of client
devices, etc. For example, in one implementation, a reference
carrier that is within close proximity to available bandwidth can
incorporate one or more carrier extensions/segments, thereby
improving overall network bandwidth.
[0062] In another variant, the aggregated bandwidth is further
organized in a manner to improve overall reception. For example, in
one such embodiment, one or more portions of the aggregated
bandwidth are allocated or de-allocated for Cell-specific Reference
Signals (CRS). Removing CRS resources can provide multiple benefits
for network operation. Firstly, CRS-free carrier types reduce
overall interference attributed to the CRS transmissions (both
inter-cell and intra-cell interference).
[0063] Moreover, resources that would otherwise be reserved for CRS
operation can be allocated to e.g., data or control traffic.
Finally, CRS-free carrier types can reduce overall power
consumption (CRS transmissions are always on, even when the cell is
not fully loaded). However, a certain portion of CRS resources are
minimally required to assist in calculations such as channel
estimation, mobility measurements, and time/frequency tracking.
[0064] In some circumstances, CRS resources are replaced with
equivalent functionality offered by alternate data and control
channel signaling. For example, certain properties of CRS can be
replaced with equivalent properties of the Demodulation Reference
Signals (DM-RS). DM-RS are specific to the client device, and thus
can be optimized based on client device performance. For instance,
a device that has very high reception quality can operate with
fewer DM-RS resources. Similarly, during periods of relatively low
usage, fewer resources can be directed to DM-RS operation.
[0065] In other scenarios, one or more portions of the aggregated
bandwidth are organized into guard bands (i.e., guard bands do not
carry traffic, and merely serve to reduce the effects of
interference). By carefully positioning guard bands at the edges of
the aggregated bandwidth, receiver complexity and processing burden
can be significantly reduced. For instance, providing a contiguous
extent of bandwidth (as opposed to a non-contiguous bandwidth)
greatly simplifies transceiver operation (only a single receiver
filter, etc.) and processing (only a single Fast Fourier Transform
(FFT)). Unfortunately, guard band placement requires fine timing
and frequency synchronization which may not always be possible;
thus, the benefits of guard band organization may in certain cases
need to be balanced with the overall cost or feasibility of
synchronization.
[0066] In another such embodiment, one or more portions of the
aggregated bandwidth are allocated for Primary Synchronization
Symbols (PSS) and Secondary Synchronization Symbols (SSS). PSS and
SSS assist in timing by providing a time reference, but are
otherwise unused for data and control traffic. Thus, PSS and SSS
can be reduced for systems which are well synchronized; however it
is appreciated that where synchronization is poor, overall
performance improvement may require significantly more resources
allocated for PSS and SSS signaling.
[0067] At step 106 of the method 100, the one or more reference
carriers and one or more carrier extensions/segments are
provisioned in accordance with the carrier
alignment/aggregation.
Example Operation--
[0068] As a brief aside, existing proposals for new carrier types
in wireless standards such as 3GPP LTE Release 11 do not have to be
backward compatible with legacy carriers. For example, legacy
constructs such as the Physical Downlink Control Channel (PDCCH),
Cell-specific Reference Signals (CRS), Physical Broadcast Channel
(PBCH), Primary Synchronization Signals (PSS), Secondary
Synchronization Signals (SSS), etc. may be allocated differently,
scheduled differently, and/or removed altogether. Unfortunately,
without further enhancements in the downlink control channels, such
modifications must rely on cross carrier scheduling from a legacy
carrier (i.e., a legacy carrier must be used to indicate the
idiosyncrasies of the non-backward compatible carriers). This cross
carrier scheduling is undesirable for multiple reasons which will
be evident to those of ordinary skill in the wireless arts.
[0069] In contrast, various solutions provided by the present
disclosure provide significant improvements over existing
proposals, in that a carrier extension/segment can append
additional resource blocks to a component carrier while still
advantageously retaining the backward compatibility of the primary
carrier. The disclosed carrier extensions/segments are useful in
practical deployments, such as where the size of the available
frequency block does not match the provisioned bandwidths of 1.4,
3, 5, 10, 15 and 20 MHz. In practical deployment scenarios, the
frequency gap between the reference carrier and the carrier
extension/segment may be excessively large. In such deployments,
the carrier extension/segment may additionally require frequency
synchronization and slot/subframe alignment (time), which must be
handled with additional control signaling overhead.
[0070] In one embodiment, the carrier extensions/segments can be
added without CRS (which are wideband common reference signals),
and instead provide CRS functionality via UE-specific reference
signals (which are narrowband and dedicated reference signals).
During operation, the UE-reference signals (e.g. a Demodulation
Reference Signal (DM-RS), Channel State Information Reference
Signals (CSI-RS), etc.) is used for channel estimation and coherent
detection of control and data channels. In some embodiments, the
CRS (or a similar wideband synchronization signal), or an
abbreviated version thereof, may be required on the carrier
extension/segment for path loss (and/or Reference Signal Received
Power (RSRP), Reference Signal Received Quality (RSRQ))
measurements that can be used for mobility management, triggering
handover, and activation and deactivation of carrier operation.
[0071] The reference carrier and the one or more carrier
extension/segment may be aligned in time, based on e.g., symbols,
slots, subframes, etc. For Orthogonal Frequency Division Multiple
Access (OFDMA) operation, the timing error can be resolved by the
cyclic prefix; i.e., the longer the cyclic prefix, the more the
timing error that can be tolerated. However, generally, the cyclic
prefix length is a constraint of the system, thus, within the
context of 3GPP LTE, the timing synchronization between the
reference carrier and the one or more carrier extensions/segments
may not exceed the capabilities of the cyclic prefix. More
directly, the mobile device can use the cyclic prefix to logically
advance or retard the carrier extensions/segments to a common time
base. While each carrier extension/segment may have a different
number of cyclic prefix (and suffix) bits, by removing the cyclic
prefix bits, each carrier is effectively time shifted back to a
common time base. For example, a carrier extension/segment which
has arrived later in time will have more cyclic prefix bits than
the other carrier extensions/segments; by removing the extra cyclic
prefix bits the later arriving carrier extension/segment is time
aligned to the other carrier extensions/segments.
[0072] Time alignment simplifies certain operations; for example,
Hybrid Automatic Repeat Request (HARQ) timing and operation, as
well as resource assignments for the reference carrier and the
carrier extensions/segments. In particular, by ensuring that both
the reference carrier and the carrier extensions/segments are
synchronized, the aggregated bandwidth can be treated as having a
common time base. A common time base is necessary to perform a
Fourier Transform; thus, a single FFT element can be used to
process a synchronized reference carrier and its associated one or
more carrier extensions/segments (i.e., rather than requiring
distinct FFT for each distinct time base).
[0073] Similarly, frequency alignment greatly simplifies
transceiver operation. Since a Fourier Transform requires regular
subcarrier spacing, maintaining similar subcarrier spacing ensures
that a single FFT can be performed. In one such embodiment, the
frequency separation between the frequency-contiguous reference
carrier and the carrier segment/extension is configured for an
integer multiple of 300 kHz, consistent with existing LTE
specifications. Similarly, the center frequencies are integer
multiples of the LTE channel raster (i.e., 100 kHz). It is further
appreciated that the foregoing spacing widths are chosen merely to
conform to the LTE specification; other wireless technology
standards with which the disclosed embodiments are useful may have
different spacing widths.
[0074] Moreover, for deployments which are not at appropriate
frequencies, then frequency offsets can be specified to align the
center frequencies. In one such embodiment, the offsets can be
predefined and signaled via RRC messages. By providing a scheme for
synchronizing timing and frequency synchronization among
non-continuous carriers, the provisioning and use of PSS and SSS on
the carrier extensions/segments can be greatly reduced.
[0075] Depending on the relative location of the reference carriers
and the one or more carrier extensions/segments in the frequency
domain, at least three distinct configuration/usage scenarios are
described: (i) where the reference carrier and the one or more
carrier extensions/segments are not contiguous in the frequency
domain, (ii) where the reference carrier and the one or more
carrier extensions/segments are contiguous in the frequency domain,
(iii) and where the reference carrier and the one or more carrier
extensions/segments are contiguous in the frequency domain and
guard band operation can be modified.
[0076] In the following discussions, the carriers (reference and
extensions/segments) are sufficiently synchronized in the time and
frequency domains regardless of the relative location of the
frequency bands. Moreover, while the enclosed figures provide
example configurations for two carrier extensions/segments, the
proposed scheme can be extended to an arbitrary number of carrier
extensions/segments. Furthermore, within the context of LTE
systems, the aggregated number of resource blocks (e.g., reference
carriers, the carrier extensions/segments, and optional guard
bands) must be less than 110. This limitation is due to existing
LTE limitations, which would not apply for other wireless
technologies, and conceivably future incarnations of LTE.
[0077] Finally, as described herein, the carrier
extensions/segments do not maintain a Cell-specific Reference
Signal. Rather, the carrier extensions/segments exclusively use
Demodulation Reference Signals (DM-RS) for channel estimation and
coherent detection of the control and data channels. In one such
variant, the carrier extensions/segments are further configured to
use a Physical Downlink Control Channel (PDCCH).
[0078] Referring now to FIG. 2, a first exemplary scenario is
illustrated, wherein the reference carrier and the one or more
carrier extensions/segments are not contiguous in the frequency
domain. As shown, if the channel separation is excessively large,
then each carrier must include time/frequency synchronization
signals (PSS/SSS), and the guard bands cannot be used for
control/data transmission. Furthermore each carrier
extension/segment must contain UE-specific reference signals
(DM-RS, and CSI-RS). The CSI-RS can be used for channel state
information (CSI) measurements and path loss measurements that can
be useful in triggering activation/deactivation of the carrier
extensions/segments.
[0079] FIG. 3 illustrates a second exemplary scenario, wherein the
reference carrier and the one or more carrier extensions/segments
are contiguous. As shown, the channel separation is not excessively
large to the extent that additional time/frequency synchronization
is required for the new carrier types. Consequently, the one or
more carrier segments/extensions do not require a distinct PSS/SSS.
In this scenario, the UE-specific reference signals and CSI-RS are
configured on the carrier extensions/segments, however the guard
band resource blocks are still dispersed throughout the bandwidth.
FIG. 3 notably does not have any backward compatibility
implications, as the spectral filtering and emission masking are
performed consistent with legacy compatibility (e.g., LTE)
[0080] Referring now to FIG. 4, where the backward compatibility is
not required, aggregated bandwidth can be further organized so as
to move the guard band resource blocks to the periphery of the
bandwidth. As shown in FIG. 4, the spectral filtering and the
emission masking at the edges of the carriers are increased
proportionate to the size of the aggregated transmission bandwidth.
This proportionate increase in guard band size ensures that legacy
UEs can still operate without interruption. In alternate variants,
the guard band size can be decreased, if the legacy UEs are limited
only to a subset of the frequencies (i.e., legacy UEs are only
scheduled within the center of the aggregated bandwidth). In FIG. 4
(as in FIG. 3), the one or more carrier extensions/segments do not
require a PSS/SSS and rely exclusively on UE-specific reference
signals and CSI-RS for e.g., channel estimation, etc. The
UE-specific reference signals and CSI-RS may be further extended
over the guard bands and the one or more carrier
extensions/segments. The aggregated total bandwidth can be operated
as a virtualized wideband carrier.
[0081] More generally, for the scenario where two carrier segments
are deployed with 5 MHz of bandwidth, next to a reference carrier
having a 10 MHz bandwidth. The aggregated carrier can be configured
as a 20 MHz carrier by appending the carrier segments on the left
and the right side of the reference band. Moreover, by removing the
legacy guard bands, and increasing the size of the left and right
guard bands, the aggregated carrier can comply with 20 MHz legacy
carriers.
[0082] It will also be readily recognized by ones of ordinary skill
in the related arts (when given the present disclosure) that other
configurations of the guard bands and the transmission bands are
also possible, as long as the resulting combination remains
consistent with desired RF and spectral emissions behavior (legacy
or otherwise).
Exemplary User Equipment (UE) Apparatus--
[0083] Referring now to FIG. 5, exemplary client or UE apparatus
500 useful in implementing the methods of the present disclosure is
illustrated. As used herein, the terms "client" and "UE" include,
but are not limited to cellular telephones, smartphones (such as
for example an iPhone.TM.), wireless enabled personal computers
(PCs), such as for example an iMac.TM., Mac Pro.TM., Mac Mini.TM.
or MacBook.TM., and minicomputers, whether desktop, laptop, or
otherwise, as well as mobile devices such as handheld computers,
PDAs, personal media devices (PMDs), or any combinations of the
foregoing. The configuration and usage of extensible carrier
resources is preferably performed in software, although firmware
and/or hardware embodiments are also envisioned; this apparatus is
described subsequently herein with respect to FIG. 5.
[0084] The UE apparatus 500 includes a radio modem or transceiver,
a processor subsystem 505 such as a digital signal processor,
microprocessor, field-programmable gate array, or plurality of
processing components mounted on one or more substrates 508. The
processing subsystem may also include an internal cache memory. The
processing subsystem 505 is connected to a memory subsystem 507
including memory which may for example, include SRAM, flash and
SDRAM components. The memory subsystem may implement one or a more
of DMA type hardware, so as to facilitate data accesses as is well
known in the art. In the illustrated embodiment, the processing
subsystem additionally includes subsystems or modules for
determining the appropriate reference carrier and one or more
carrier extensions/segments, and configuring operation thereto.
These subsystems may be implemented in software or hardware which
is coupled to the processing subsystem. Alternatively, in another
variant, the subsystems may be directly coupled to the digital
baseband.
Exemplary Base Station (BS) Apparatus--
[0085] Referring now to FIG. 6, exemplary server or base station
(BS) apparatus 600 useful in implementing the methods of the
present disclosure is illustrated. As used herein, the terms
"server" and "BS" include, but are not limited to base stations
(e.g., NodeB, eNodeB, etc.), access points, relay stations, etc.
The configuration of one or more reference carriers and/or one or
more carrier extensions/segments is preferably performed in
software, although firmware and/or hardware embodiments are also
envisioned; this apparatus is described subsequently herein with
respect to FIG. 6.
[0086] The BS apparatus 600 includes a wireless modem or
transceiver, a processor subsystem 605 such as a digital signal
processor, microprocessor, field-programmable gate array, or
plurality of processing components mounted on one or more
substrates 608. The processing subsystem may also include an
internal cache memory. The processing subsystem 605 is connected to
a memory subsystem 607 including memory which may for example,
include SRAM, flash and SDRAM components. The memory subsystem may
implement one or a more of DMA type hardware, so as to facilitate
data accesses as is well known in the art. In the illustrated
embodiment, the processing subsystem additionally includes
subsystems or modules for implementing the various schemes for
alignment and aggregation of carriers as described previously
herein. These subsystems may be implemented in software or hardware
which is coupled to the processing subsystem. Alternatively, in
another variant, the subsystems may be directly coupled to the
digital baseband.
[0087] It will be recognized that while certain embodiments of the
present disclosure are described in terms of a specific sequence of
steps of a method, these descriptions are only illustrative of the
broader principles described herein, and may be modified as
required by the particular application. Certain steps may be
rendered unnecessary or optional under certain circumstances.
Additionally, certain steps or functionality may be added to the
disclosed embodiments, or the order of performance of two or more
steps permuted. All such variations are considered to be
encompassed within the present disclosure and claimed herein.
[0088] While the above detailed description has shown, described,
and pointed out novel features applied to various implementations,
it will be understood that various omissions, substitutions, and
changes in the form and details of the device or process
illustrated may be made by those skilled in the art without
departing from the principles described herein. The foregoing
description is of the best mode presently contemplated of carrying
out the principles described herein. This description is in no way
meant to be limiting, but rather should be taken as illustrative of
the general principles. The scope of the present disclosure should
be determined with reference to the claims.
* * * * *